The effect of the in-medium $Θ^+$ pentaquark on the kaon optical potential

Abstract

The kaon nuclear optical potential is studied including the effect of the $Θ^+$ pentaquark. The one-nucleon contribution is obtained using an extension of the Jülich meson-exchange potential as bare kaon-nucleon interaction. Significant differences between a fully self-consistent calculation and the usually employed low-density $Tρ$ approach are observed. The influence of the one-nucleon absorption process, $K N \to Θ^+$, on the kaon optical potential is negligible due to the small width of the pentaquark. In contrast, the two-nucleon mechanism, $K N N \to Θ^+ N$, estimated from the coupling of the pentaquark to a two-meson cloud, provides the required amount of additional kaon absorption to reconcile with data the systematically low $K^+$-nucleus reaction cross sections found by the theoretical models.